Device for drawing elliptical paths

ABSTRACT

AN ELLIPSE DRAWING INSTRUMENT HAVING TWO SLIDING MEMBERS SLIDABLE LONGITUDINALLY IN CROSSING SLOTS. THE SLIDING MEMBERS ARE PIVOTABLY CONNECTED TO A SINGLE DRAWING ARM, SO THAT AS SAID MEMBERS RECIPROCATE IN THEIR RESPECTIVE SLOTS, A POINT ON THE ARM DESCRIBES AS ELLIPTICAL PATH.

Feb. 16, 1971 BROWN 3,562,915

DEVICE FOR DRAWING ELLIPTICAL PATHS Filed May 6, 1969 United StatesPatent Oflice 3,562,915 Patented Feb. 16, 1971 3,562,915 DEVICE FORDRAWING ELLIPTICAL PATHS George Brown, Welwyn Garden City, England,assignor to Ellipstruments Limited, Harpenden, England, a Britishcompany Filed May 6, 1969, Ser. No. 822,278 Claims priority, applicationGreat Britain, May 7, 1968, 21,602/68 Int. Cl. B43l 11/04 U.S. Cl. 33312 Claims ABSTRACT OF THE DISCLOSURE An ellipse drawing instrument havingtwo sliding members slidable longitudinally in crossing slots. Thesliding members are pivotably connected to a single drawing arm, so thatas said members reciprocate in their respective slots, a point on thearm describes an elliptical path.

The present invention relates to an instrument for facilitating thedrawing of ellipses, and elliptical paths.

In, for example, technical and geometrical drawings it is frequentlynecessary to construct an ellipse, in part or whole, and to accuratelyrelate the size and position of the ellipse to the rest of the drawing.

There are several known drawing procedures for constructing such anelliptical path but they are generally painstaking, time consuming and,unless great care is taken, inaccurate.

There are also known devices for aiding the drawing of an ellipse, forexample the well known piece of string or cord looped around a pair ofspaced pins, but they are mostly clumsy to operate and it is difficultto accurately reproduce an ellipse of a required size.

An object of the present invention is to provide a device or instrumentfor drawing ellipses which is simple to use and which can be easily andreadily adjusted to reproduce an ellipse of a required size.

The present invention consists in an ellipse drawing instrumentcomprising a drawing arm, and a pair of members adapted to be pivotablyconnected to said drawing arm at two spaced points on the drawing arm,one of said members being constrained to move along a first path and theother of said members being constained to move along a second pathcrossing the first path so that in use, as said members reciprocatealong their respective paths, a point of said arm describes anelliptical path.

Preferably, said paths are linear and perpendicular to each other, andare provided in two spaced parallel planes by guide slots in a commonbase. The members slide in said slots.

A drawing instrument can be guided by said arm to construct anelliptical path or drawing means can be attached to said arm.

Said points on said drawing arm can be infinitely adjustable toconstruct an ellipse of a given size within a range determined by thesize of the instrument.

The invention will now be described by way of example with reference tothe accompanying drawings which shows a perspective view of aninstrument according to the invention.

Referring to the drawing, an ellipse drawing instrument 1 comprises abase 2 on which move sliding members 3, 4 for guiding a drawing arm 5.

The base 2, preferably of plastics material, is provided with a firstretaining slot 6 which extends transversely of the base. Slot 6accommodates member 3 and the relative sizes of the member 3 and slot 6are such that member 3 is freely slideable longitudinally in the slotwith a minimum of lateral play.

Extending longitudinally of the base 2 is a second retaining slot 7,which accommodate sliding member 4. However, whereas slot 6 is formed inthe base 1 so that member 3 when in the slot is substantially flush withthe upper surface of the base 1, slot 7 is defined by projections 9, ofgenerally inverted L shape in cross-section, attached to said uppersurface so that the plane of movement of sliding member 4 is above thebase 2. Thus the sliding member 4 is constrained from all butlongitudinal sliding movement when in slot 7, being held in said slot byoverhang 10 of projections 9. Projections 9 are arranged in two pairs,one pair on each side of the transverse slot 6 so that there is acentral gap in slot 7 where it crosses over slot 6. However, theprojections 9 extend over the edges of the slot 6, as at 8, sufficientlyto retain sliding member 3 in slot 6.

Projections 9 are preferably formed integral with the base 2, the basewith the projections 9 and slot 6 being, say, moulded by any convenientknown method. However the projections 9 can be formed by building up therequired cross-section on an already formed base.

Sliding members 3, 4 are preferably of plastics material and are a closesliding fit in their respective slots 6 and 7. Both members 3 and 4 arepointed at their ends 11 to assist initial setting of the device on adrawing board as will be outlined hereinafter. Centrally disposed oneach member 3 and 4 is a cylindrical projection 12, 13 respectively, ofsuch different heights that the tops of said projections 12 and 13 arein the same horizontal plane when the device is assembled. Eachprojection 12 and 13 is provided with an axial bore 14.

In this embodiment the member 4 is considerably smaller in size than themember 3. This is not imperative to the working of the invention but isa preferred feature, the point being to minimise the width of member 4so as to give a minimum of interference between the projection 12 ofmember 3 and the body of member 4 when member 4 is in a positionbridging slot 6.

Apart from this interference, members 3 and 4 are free to moveindependently in their respective guide slots.

Drawing arm 5 comprises two spaced parallel track members 15 formed froma length of stiff steel wire which is bent through at a pointintermediate its ends, which point then forms one end 16 of the arm 5.At the other end of arm 5, the free ends of the length of wire areclamped by an arrangement 17 which comprises two clamping washer plates18 and a drawing extension 19, held together by a threaded pin and nutor by any other equivalent means for example riveting.

Drawing extension 19 extends downwardly from the arm 5, the tip 20 ofthe extension being parallel to the plane of the base 2 and having asmall aperture formed therein through which the point of a drawinginstrument can project.

Intermediate the ends of arm 5 are mounted two elements 21 and 22, eachhaving a pin 23 extending downwardly from arm 5 between track members15. Each element comprises a pair of washers between which pass thetrack members 12 of arm 15, and pin 23 extends up through the washers toterminate in a cap 24. The lower washer is fixed to the pin and theother upper washer is biassed away from cap 24 by a coil spring. Thusthe washers are forced towards each other to clamp said track members 15therebetween. It will be realised that each element 21 and 22 can bemoved longitudinally of arm 5 but that when in a required position onthe arm each element will be effectively held against any accidentalmovement by the spring-biassed washer clamping action.

The downwardly projecting pins 23 of elements 21, 22 engage in the axialbores of projections 12, 13 respectively on sliding members 3, 4. Toachieve maximum accuracy from the device play between said pins and boreshould be kept to a minimum.

The base 2 is provided with four through apertures 25 by means of whichit can be pinned to, say, a drawing board to facilitate use of theellipse drawing instrument.

To draw an ellipse of a given size the instrument is used as follows.

Elements 21 and 22 are adjusted on arm 5 so that the distance betweenthe aperture in tip of the arm and element 21 equals half the length ofthe major axis of the required ellipse, and the distance between saidaperture and element 22 equals half the minor axis of said ellipse. Itfollows that element 22 will always be that element nearer the extension19.

The instrument is preferably pinned down to a drawing board by pinsextending through apertures 25 of the base. As this is done the pointedends 11 of sliding member 3 are aligned with the direction of the minoraxis of the ellipse to be drawn and the pointed ends of sliding member 4with the direction of the major axis of said ellipse. With theinstrument thereby correctly placed, as required, on the drawing board,an elliptical path 26 is drawn by inserting the drawing point of apencil 27 or other drawing instrument in the aperture of drawingextension 19 and moving the pencil so as to rotate arm 5. As the arm 5is rotated, sliding members 3 and 4 reciprocate in their respectiveslots and constrain the pencil, via arm 5, to move in an ellipticalpath.

It will be realised that a complete ellipse can be drawn in one movementor only part of one, as desired. Further, if no measurements are knownof the axes of an elliptical path to be drawn the position of elements21 and 22 of the instrument can of course be set by a trial and errormethod.

The instrument can be readily dissembled into separate component parts,namely the base, two sliding members and drawing arm, for packing andstorage purposes.

An instrument according to the invention need not have the slots of thesliding members at right angles to one another. However, if said slotsare inclined relative to one another at some angle other than 90 thegeometrical axes of an ellipse drawn by the instrument will not be inthe same direction as the axes of the slots.

Various modifications are possible within the scope of the invention,for example a drawing instrument, say

a piece of lead, could be permanently attached to the end of saiddrawing extension, or the drawing extension made adjustable in positionon arm 5.

I claim:

1. An ellipse drawing instrument comprising a relatively small base,means defining a first linear path in said base, means defining a secondlinear path on said base crossing said first path and being disposed ina separate horizontally extending plane relative to the plane of saidfirst path, a first elongated sliding member slidingly accommodated insaid first path, and being longer than said first path, a secondelongated sliding member slidingly accommodated in said second path andbeing shorter than said first member, the ends of each member beingpointed for alignment with ellipse major and minor axes, projectionmeans upstanding from each of said members intermediate its ends, anelongated, longitudinally-slotted drawing arm receiving said projectionmeans, resiliently-urged clamping means on each of said projectionmeans, resiliently engaging said arm whereby said arm is readilyslidably maintained in a plane parallel to said base as said slidingmembers are reciprocated in said paths, and mounting means at one end ofsaid arm adapted to receive a pencil tip.

2. An instrument according to claim 1 wherein said paths are mutuallyperpendicular and said mounting means positions said pencil tip in theplane of said base.

References Cited UNITED STATES PATENTS 717,082 12/1902 Dart 33-311,031,780 7/1912 Fine 3331 2,082,065 6/1937 Knackert 33--31 1,021,5833/1912. Dzierwa 3331 3,032,893 5/1962 Debeh 33-31X FOREIGN PATENTS218,013 1/1910 Germany 3331 178,253 9/1935 Switzerland 3331 OTHERREFERENCES Popular Science, April 1945, page 168.

HARRY N. HAROIAN, Primary Examiner

